1. Field of the Invention
The present invention relates to a liquid light-duty detergent composition. More particularly, the invention relates to a liquid light-duty detergent composition containing a cationic surface active agent. The composition is capable of imparting a soft finish to washed clothes. The composition is a homogeneous transparent liquid. The inherent defect of conventional detergent compositions of this type, namely, the lack of an antiredeposition effect, is overcome by the use of a combination of a specific fatty acid diethanolamide and a specific amphoteric surface active agent.
2. Description of the Prior Art
Sweaters, cardigans, holiday garments, formal clothing, evening wear and the like made of wool or chemical fibers have heretofore been customarily washed with light-duty detergents comprising, as a main surfactant component, a linear dodecylbenzenesulfonate, an alkylsulfate, an .alpha.-olefinsulfonate or mixture thereof. These main surfactant components are materials which are customarily used in heavy-duty detergent compositions, and they are not suitable for washing sweaters, cardigans, holiday garments, formal clothing, evening wear and the like for which a soft finish is required. Therefore, various light-duty detergent compositions containing a cationic surface active agent, which has been used as a fiber-softening agent, have heretofore been proposed in the art. For example, there can be mentioned (1) a detergent composition comprising a non-ionic surface active agent, a sulfobetaine, an amine oxide, coconut fatty acid diethanolamide, a builder, di-(tallow alkyl)dimethyl ammonium chloride and a specific polymeric compound (U.S. Pat. No. 3,537,993), (2) a detergent composition comprising a specific amine oxide and a specific cationic surface active agent (Japanese Patent Publication No. 4750/72 corresponding to U.S. Pat. No. 3,849,348), and (3) a liquid detergent composition formed by adding ethanol and water to a composition comprising a specific cationic surface active agent and a non-ionic surface active agent and/or an amine oxide (West German Laid-Open Specification No. 2,426,581).
As a result of our investigations made on these detergents, it was found that each of them is not completely satisfactory because of a lack of a sufficient antiredeposition property. Solid dirt particles are negatively charged in an aqueous washing liquor, and if the liquor contains a cationic surface active agent, it is absorbed on the negatively charged solid dirt particles with the hydrophobic group of the cationic surface active agent protruding toward or facing the water side. Therefore, the particles undergo sedimentation or cohesion, and they are finally deposited on the fibers, i.e., the dirt is redeposited on the fibers. This defect cannot be eliminated in conventional detergents comprising a cationic surface active agent.
It is therefore a primary object of the present invention to provide a liquid light-duty detergent composition in which this defect is eliminated and a good antiredeposition effect and washing power can be attained.
In general, it is very difficult to obtain a homogeneous transparent detergent containing a cationic surface active agent. For example, it is difficult to incorporate even a small amount of di-(tallow alkyl)dimethyl ammonium chloride stably in a solution or dispersion phase. There have heretofore been proposed stable fiber-softening compositions including the combination of an anionic fluorescent dye and a dialkyl quaternary ammonium salt (Japanese Patent Publication No. 35637/73), the combination of a polyethenoxy quaternary ammonium salt and a dialkyl quaternary ammonium salt (Japanese Patent Publication No. 41095/73) and the combination of a carboxybetaine, a non-ionic surface active agent, a polyethenoxy quaternary ammonium salt and a dialkyl quaternary ammonium salt (Japanese Patent Publication No. 10439/75 corresponding to U.S. Pat. No. 3,862,045). Further, West German Laid-Open Specification No. 2,426,581 proposes a stable detergent composition including a di-(tallow alkyl) quaternary ammonium salt. According to these proposals, however, it is impossible to obtain a transparent liquid softener or detergent that is stable at low temperature.
It is therefore a secondary object of the present invention to provide a stable liquid light-duty detergent capable of maintaining a transparent state even at low temperature.
In general, clothes washed with a detergent comprising a cationic surface active agent are soft and have a good feel, but this effect may be lost if some kinds of additives are incorporated in the detergent composition. For example, an anionic surface active agent or some specific non-ionic surface active agents drastically degrade the softening effect of the cationic surface active agent.
It is therefore a third object of the present invention to provide a liquid light-duty detergent in which the softening effect of the cationic surface active agent is not degraded, but rather is maintained at a high level.